Throughout the darkest period of his life--when he was banished to a remote work farm, separated from his wife and daughter, forbidden to practice his profession as a lawyer, threatened with death, held in solitary confinement--Ma Rongjie kept telling himself that someday his government would need him again and ask him to serve.

He was right. But Ma, one of China's foremost legal experts, could not foresee that his comeback would involve defending the very people who had sanctioned his ordeal of terror.

After 10 years of persecution as a counterrevolutionary outcast during China's Cultural Revolution, Ma was appointed chief defense counsel at the trial of China's "Gang of Four."

It was not a case that he embraced with relish. "I did not like to do this case ," said Ma, a visiting law professor at the University of Minnesota who was in Washington this past week. "Everybody hated them because they did things which are very bad.

"But I am lawyer. I must forget they were bad to me, very bad to many people. It is task. I must do," explained Ma, who is the first Chinese legal scholar to be allowed by his government to teach for an academic year in the United States. His program is funded by a half-dozen multinational corporations, university officials said.

Ma, an exuberant and outgoing man, was 16 years old when the Communists came to power in 1949 and, as part of their Marxist revolution, introduced a new kind of legal system in which all lawyers are salaried government employes.

Ordered by the authorities to study law, Ma was not enthusiastic at the time. "I did not like law school because I thought, there is no law in China, what would I do? But at that time in China, everything was for the people, for the country, so I could not say I won't go. It is task. I must go," Ma said.

In those early years while the new Communist government was training its own legal cadres, Ma was one of only three lawyers in China and today, to serve a population of almost 950 million, he is one of about 5,500, he said.

When the Red Guards, led by Chairman Mao Tse-tung's wife, Jiang Qing, and the rest of the Gang of Four unleashed the Cultural Revolution across China in 1966, Ma, like many intellectuals, was denounced as a criminal. "They said I was a criminal because I defended criminals. It is very strange logic," he said.

Ma spent 10 months in solitary confinement, was shipped to a hard labor camp and finally to a remote collective farm where he sat out the turmoil of the Cultural Revolution without his family. He consoled himself by thinking of the future. "I know my country. Is very big. Many people. We need law. So I knew one day they need me again. So I said I will keep myself. I will not kill myself. A lot of people, they kill themselves in that time," he said scraping his finger across this throat.

During the reign of the Gang of Four, "there was no law. The Gang of Four did not need law. Anything they said, that's law, so law was broken. Including the constitution. They threw the constitution away. That's very terrible. You could not feel safe in my country," said Ma.

When the Gang of Four "was broken" in 1976, the government "remembered Mr. Ma and they said, 'Come back,' " he recalled. Ma was appointed to the Legal Research Institute at the Chinese Academy of Social Sciences where he still works, and in 1980 was asked to head the 18-member defense team at the Gang of Four's trial.

As is customary in Chinese criminal cases, the guilt of the Gang of Four was pretty well determined before the trial began. Ma's defense task was to sort out the truths and what he called "half-lies" in the prosecutor's allegations and then try to mitigate, through legal arguments, the responsibility of each defendant. For example, Ma said, it was alleged the defendants "hoped to kill Chairman Mao. But Chairman Mao's wife, she did not want to do this. She did not want to kill Mao. So this was not her problem. But she did other crimes."

All the defendants (there were five others in addition to the Gang of Four) got heavy prison sentences, and Jiang, then 67, was condemned to death. Her sentence was postponed for two years pending good behavior, and Ma believes she will not be executed. "I think they don't put the widow dead. If we put her dead, we would not wait two years."

When Ma returns to China he will concentrate on international trade and commercial litigation, a field that has boomed since China adopted an open door policy in trade relations with the West. He already is closely involved with most contracts signed between his government and multinational companies.

Ma, who was escorted around the U.S. Supreme Court by Chief Justice Warren Burger on one visit to Washington, said he has been surprised by many things in this country and heading the list is "terrible tax. Taxes are very big. In China, no taxes. I got money from the law school but high tax, so I must ask the tax professor what I should do about taxes. I could not do myself."

He also finds American legal practices different. "Your lawyers only do one thing, but in our country, if you are a lawyer, you must do many things, criminal cases, civil and international trade. It's easier than your country because the laws are very few in China .

"In your country, many, many books. I ask many lawyers, 'What should you do in this case?' and they say, 'Let me look in this book, in that book.' But in my country it's no use looking in many books. I remember in my mind. I remember here," he said, tapping his temple. "Because I was a lawyer for a long time."